Single use restrooms are less safe for women and girls.
I fully understand your point, but multiple-use bathrooms also have this problem when there aren't others in there with you (not infrequent). There are some technical things you could do to protect women and girls in this context, but I don't disagree. As I said, they have them in Europe, so might be interesting to see what their experience is in this regard.
Ultimately, this is another problem created by pandering to a small group of people in order to make political points. There are other solutions that would preserve the dignity of everyone and not lead to political confrontation. You could just have the traditional women's and men's bathrooms, and then have single use bathrooms for those who don't want the public bathrooms or who are part of the ‘other’ categories. To me, I would think there would be less stigma involved in using a single-use bathroom than walking into a woman's bathroom when you are a cross-dressing man. Unfortunately, from what I've read, it seems that they are doing the opposite (everyone uses the public multiple person bathrooms, and single use bathrooms are provided to those who have a problem with sharing a bathroom with those of the opposite gender).